Sulphide, galena group
Specific gravity: 2.58
Colour: Pale brown to dark brown, colourless to pale brown in transmitted light, tarnishes strongly on exposure to humid air (Mindat)
Common impurities: Mg,Na,Fe,Cu
Due to high melting point of 2450oC, oldhamite is an early nebular condensate;
it may fill the latest interstices between silicates in enstatite chondrite and achondrite
meteorites. Associated minerals include
gypsum, calcite and
Terrestrial oldhamite is associated with pyrometamorpism, especially with coal fires. It is quite unstable in air, and hydrolysis makes it change into portlandite. It also occurs in anthropogenic blast furnace slag (Mindat).
At the type locality, the Bustee meteorite, Gorakhpur, Basti District, Uttar Pradesh, India, oldhamite occurs as single-crystal nodules, to 3 mm, in an enstatite chondrite meteorite. Associated minerals include troilite, osbornite, niningerite, gypsum, enstatite, calcite and augite (Mindat).
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